Novel hypotensive agents, niazimin A, niazimin B, Niazicin A and Niazicin B from Moringa oleifera: isolation of first naturally occurring carbamates
Two novel hypotensive carbamate glycosides designated niazimin A 1 and niazimin B 3 and two new hypotensive mustard oil glycosides possessing the thiocarbamate group, niazicin A 5 and niazicin B 10 along with a benzaldehyde glycoside 12 have been isolated from the fresh leaves extract of Moringa oleifera employing bioassay-guided fractionation. The structures of all these glycosides have been elucidated on the basis of spectroscopic evidence (IR, UV, MS, NMR, 2D NMR) and chemical reactions. Compounds 1 and 3 appear to be the first natural products embodying the carbamate moiety. The amide bond in these compounds appears to play an important role in the hypotensive activity, since in both the carbamates and thiocarbamates it is common to those which possess hypotensive activity.